Running off of generators or inverters

I ran our test specimen with blowers and feeder motor connected on the Coleman 2250 generator for a few hours with no issues or problems. The conclusion I draw from this is "do not purchase a inverter type generator for your stove if you are expecting trouble free operation". This goes for Coal-Trol units and non-Coal-Trol units equally.

I'm sure some others can shed more light as to why this is the case, and I'm sorry for those that already did purchase an inverter type generator for your stove, but I learned something today.

Matthaus wrote:I ran our test specimen with blowers and feeder motor connected on the Coleman 2250 generator for a few hours with no issues or problems. The conclusion I draw from this is "do not purchase a inverter type generator for your stove if you are expecting trouble free operation". This goes for Coal-Trol units and non-Coal-Trol units equally.

I'm sure some others can shed more light as to why this is the case, and I'm sorry for those that already did purchase an inverter type generator for your stove, but I learned something today.

Your kidding right? I would like to hear the explanation on why this is true. I never read in the manual anything about having to use a certain type of generator. Maybe if I ever get my replacement col-trol I'd have a better outlook on the stove. Until proven differently I would be more happy with manual stove controls that were reliable and accepting of all types of generator types than my current unreliable col-trol that most likely won't work with my inverter generator that is supposed to be cleaner power for electronics. Oh,Matt, its been over 2 weeks since you said you would send a replacement col-trol and haven;t seen it yet....no rush though,it's only the middle of December here in Maine and the stove is my primary heat source.

Your kidding right? I would like to hear the explanation on why this is true. I never read in the manual anything about having to use a certain type of generator.

Inverter generators have a limitation many folks do not understand. Their output is "generated" using high speed MOS switching transistors that have an absolute current limit. Hit that limit and the output drops out briefly or full shutdown based upon the design. This is to prevent burning out the MOS transistors. (I'm assuming a sine wave inverter generator, if modified sine wave, all bets are off)

Virtually all modern shaded pole motor speed controls use switching the motor supply on and off during each AC cycle to modulate motor speed.

A shaded pole motor never runs synchronous to the AC frequency input, it has some "slip". Add a speed control (other than a 1950 switched inductor manual unit or a magnetic amplifier) and the slip increases dramatically, needed to slow the speed. That means, when the speed control cuts in, the motor virtually always is not in phase with the supply. Such a situation causes significant current spikes.

(Other devices powered off the generator can also cause current spikes)

This may cause an inverter generator to cut out or the current spikes may cause a very dirty waveform. The dirty waveform can even occur from a conventional alternator, the resistance of an alternator (usually called a generator) is not nearly as low as as the utility company.

Many devices have problems with inverter generators (and sine wave inverters without sufficient surge capacity)! Almost any device with a switching power supply - Computers, modern TVs... all have non uniform current waveforms. They ALL cause current spikes. Heck, my camper's electronic AC to DC converter causes my 1200W inverter generator to shut down! My el-cheapo 1100 Watt conventional generator (alternator) has no problems with it.

Inverter generators just can't handle loads that cause current spikes well unless grossly over sized or over designed. They will run incandescent light bulbs (no spikes) just fine.

Unfortunately, the most modern generators (inverter) are a poor choice for many modern loads that use electronic switching. These same modern loads will almost always make conventional generator's output look dirty due to the resistance of the generator being much higher than the utility company's drop.

gerry_g, has it right. Inverter generators or even UPS inverters work fine with resistive loads, i.e. incandescent light bulbs. Anything else especially inductive loads, i.e., motors, switching power supplies, cause the current drawn not to be in phase with the supplied voltage. Current spikes result, which produces large voltage spikes when there are inductors. These will trigger any protection circuits to the off state. Or if they continue will over time puncture the enamel insulation on your motor windings. Don't use them.

If you must use them get a dual trace oscilloscope and look at both the applied voltage and resulting current drawn. Filter appropriately. This requires engineering skill which most here will not have.

If you must have a no utility power capable coal appliance here's what you can do. Replace your motors with DC motors. You know the ones with brushes. Decades ago they were called AC/DC universal motors. Connect those DC motors to a deep discharge battery. Then continuously charge those batteries with a utility powered battery charger. Select the battery size based on the amp hours needed. Complicated yes. There is no free, cheap lunch.

Yanche,

Could you repost this as its own topic and maybe have it as a sticky.

There have been numerous questions about generators vs. grid power and numerous posts about UPS's. I think it needs to be brought out front and not hidden here in this thread.

I for one appreciate that you and gerry_g have finally given the reasons for generator problems.




Rick

Yanche wrote:gerry_g, has it right. Inverter generators or even UPS inverters work fine with resistive loads, i.e. incandescent light bulbs. Anything else especially inductive loads, i.e., motors, switching power supplies, cause the current drawn not to be in phase with the supplied voltage. Current spikes result, which produces large voltage spikes when there are inductors. These will trigger any protection circuits to the off state. Or if they continue will over time puncture the enamel insulation on your motor windings. Don't use them.
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Correct and one must remember that motors with ANY slip present an inductive, out of phase load.

Vintage motor speed controls were simply manually switchable inductors. They work very well preventing surges.

Magnetic amplifiers actually a variable inductor controlled by a small DC current. They are complex to design, manufacture and are heavy, don't even think of it! They are used used for expensive industrial controls and other applications such as theatrical high wattage lighting control. Dimming thousands of watts of stage lighting is not cheap.

Most electronic dimmers and speed controls are actually just electronic switches which "turn on" twice every AC cycle when they expect the sine wave supply to be at the desired voltage level. Since a motor with any slip will be out of phase with the supply, a sine wave inverter will see an abnormally high current and likely cut out. A "modified sine wave" inverter actually produces pulse outputs with a peak voltage that of a sine wave and a pulse width such that the average output is the same as that of a sine wave which varies +- from zero. There is no correct point for an electronic speed control to cut in with modified sine wave supplies.

Electronic switching doesn't hurt modern variable speed air mover fan motors. They have enough inductance to prevent motor damage but will feed back out of phase current. The problem occurs when out of phase load is fed back to inverters (or inverter generators). These have very limited ability to absorb fed back current or supply excess current surges. The MOS switching transistors have an absolute current limit and if not automatically shut down, will fry if overloaded, even if just repetitive very short spikes.

Conventional generators (alternators) are also inductive and are usually absorb switched or out of phase loads without damage. The voltage may drop (or be "dirty") or the engine stall but damage is unlikely.
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ANY modern electronic device (computers, TVs..) generally have switching power supplies. They put a "dirty" load on the supply. Again, inverters must be over sized or over designed to handle these types of loads. Computer UPS's are specifically designed to feed switching power supplies in a computer which present capacitive load. Most are modified sine wave (pulse) and thus a very poor choice for motors which are inductive loads.

The above is not fully accurate . A complete description requires advanced electrical engineering knowledge. That just happens to be my profession.

This is a VERY COMPLEX subject. a summary might be - FOR shaded pole motors:

Conventional generators (alternators) GOOD

Inverter generators (unless true sine wave and significantly over sized) BAD

gerry_g, your detailed understanding of the voltage waveshape and load current exceeds mine. Thank you for sharing it. Would you comment on the current designs for switching mode power supplied that attempt to force the power factor to unity using active electronic control. If I understand the objective it can make an inductive or capacitive load look like a resistive load.

In other threads on this forum I've suggested "cleaning up" UPS or inverter waveforms with isolation transformers. I even suggested somewhat seriously to using two identical AC arc welder transformers back to back to clean up the waveform. It seems to me the isolation transformer would be beefy enough to absorb the spikes and it's output would be close to sinewave and certainly a smooth continuous waveshape. Was this sound advise?

Yanche wrote:gerry_g, you detailed understanding of the voltage waveshape and load current exceeds mine. Thank you for sharing it. Would you comment on the current designs for switching mode power supplied that attempt to force the power factor to unity using active electronic control. If I understand the objective it can make an inductive or capacitive load look like a resistive load.

In other threads on this forum I've suggested "cleaning up" UPS or inverter waveforms with isolation transformers. I even suggested somewhat seriously to using two identical AC arc welder transformers back to back to clean up the waveform. It seems to me the isolation transformer would be beefy enough to absorb the spikes and it's output would be close to sinewave and certainly a smooth continuous waveshape. Was this sound advise?

Traditional switching power supplies have a simple diode bridge input connected to a capacitors. The inverter runs off of the capacitors. This design places a heavy current surge near the peak of the sine wave. It starts at whatever voltage the capacitors voltage as drooped to while the sine wave voltage is below capacitor voltage. These high current surges not only cause high surges but the resulting high current causes significant resistive peak voltage drop in the distribution wiring feeding the supply and nasty harmonics.

There are multiple ways to handle this problem with the improvements in MOS switching transistors.

One referenced (and diagram of conventional computer type supplies) is at

http://en.wikipedia.org/wiki/Switched-mode_power_supply

Re: using transformers - won't work. Transformers do not store energy, merely convert voltages. Expensive line conditioners exist that store energy and use it to handle imperfections in line or load.

There are much cheaper ferroresonant conditioners but they produce a very undesirable waveform (nearly a square wave, not even modified sine wave pulses). Lots of lower end camper converter/chargers are ferroresonant, the hum is obvious. The waveform would also clobber inverter generators.

Think of the surge component of conditioners as an analog to heavy flywheel added to a generator. That uses mechanical energy storage for surges.

You might be interested in

http://en.wikipedia.org/wiki/Voltage_regulator

So gerry_g,

What should we be using for back up power when we lose it from the grid ????

Is there anything that us low budget mortals can buy or create somewhat cheaply???



Rick

I would also like to add a question about this: http://www.yamaha-motor.com/outdoor/pro ... /home.aspx

It has a Pure Sine Wave (Pulse Width Modulation) Inverter System. I don't run multiple motors since I have a hand-fired, but bought this due to voltage spikes I got with a Chinese gen-set when both legs were imbalanced (fried a ballast & motion light).

I basically bought it for longevity & the fact that it's 64db at full throttle .... the inverter part was an added bonus.

Well you had better post that generators are not to be used with your stoves.

The idea that you need to purchase a pure sine wave generator to run a stove that costs half as much is ridiculous.

Do you plan to put in your literature that you cannot use a generator with your product?

cmperry wrote:

Matthaus wrote:I ran our test specimen with blowers and feeder motor connected on the Coleman 2250 generator for a few hours with no issues or problems. The conclusion I draw from this is "do not purchase a inverter type generator for your stove if you are expecting trouble free operation". This goes for Coal-Trol units and non-Coal-Trol units equally.

I'm sure some others can shed more light as to why this is the case, and I'm sorry for those that already did purchase an inverter type generator for your stove, but I learned something today.

Your kidding right? I would like to hear the explanation on why this is true. I never read in the manual anything about having to use a certain type of generator. Maybe if I ever get my replacement col-trol I'd have a better outlook on the stove. Until proven differently I would be more happy with manual stove controls that were reliable and accepting of all types of generator types than my current unreliable col-trol that most likely won't work with my inverter generator that is supposed to be cleaner power for electronics. Oh,Matt, its been over 2 weeks since you said you would send a replacement col-trol and haven;t seen it yet....no rush though,it's only the middle of December here in Maine and the stove is my primary heat source.

EXACTLY RIGHT.

I will also add that my father's ALASKA stove runs fine on generator power. I guess Alaska uses better motors in their stoves.

Rick 386 wrote:So gerry_g, What should we be using for back up power when we lose it from the grid ????Is there anything that us low budget mortals can buy or create somewhat cheaply???Rick

Purchase a cheap alternator style generator like my Coleman 2250, I bought it for $325. By the way I'm not saying you CAN"T run your Coaltrol on an inverter style generator I'm just saying they aren't tested to be run by one.

Anyone planning to run any appliance on a back up power source would be wise to test it before counting on it.

Matthaus wrote:

Rick 386 wrote:So gerry_g, What should we be using for back up power when we lose it from the grid ????Is there anything that us low budget mortals can buy or create somewhat cheaply???Rick

Purchase a cheap alternator style generator like my Coleman 2250, I bought it for $325. By the way I'm not saying you CAN"T run your Coaltrol on an inverter style generator I'm just saying they aren't tested to be run by one.

Anyone planning to run any appliance on a back up power source would be wise to test it before counting on it.

"do not purchase a inverter type generator for your stove if you are expecting trouble free operation"(Matt quote)....Sure sounds like you can't run your stove on an inverter style generator to me and is consistent with what you told me(stove won't run properly using inverter generator). This is beginning to sound like word mincing

Been discussed with many of the Battery Backup Threads and inverters and generators threads that the motors and/or Coaltrol may not function properly and/or make a humming noise from the motors, since some outputs are not TRUE Sine waves.